WWE could use Sting and Hulk Hogan at WrestleMania 31, but it will depend on physical testing. The Wrestling Observer Newsletter indicates that everyone over the age of 45 is subject to a WWE physical, which the two legends will need to pass if they are to work at Mania. Both men have expressed a desire to work at the March 29th show. The WWE decision on Hogan wrestling will be made if he can pass the physical. The stringent physical testing has existed ever since Jerry Lawler's heart attack in 2012. WWE requires all of their older talent to pass the physical before they'll let them do anything active. Vince McMahon doesn't want to risk anyone dying on his watch. The physical test is the reason that we haven't seen Hulk Hogan doing anything action related since returning to WWE. He obviously can't get past the test, with known issues like a bad hip and back. However, he has talked about now feeling better than ever. Maybe he's got himself into a position where he could pass the test. As for Sting, he's expected to debut with WWE before WrestleMania 31. Presumably he's rested up and in decent physical condition. It seems likely that he'll be working one match at WrestleMania 31. Hogan is more of a long shot. It goes without saying, both men would be a major draw for the show. They're famous superstars and lapsed / casual fans will buy shows marketed around nostalgia. The tickets for the Santa Clara show are now on sale and it promises to be a a huge extravaganza of pro wrestling.
